The present invention relates to trolleys for conveying containers for pieces or components in industrial plants, of the type comprising:                a structure provided with a plurality of wheel units, pivotable about respective vertical axes;        a trolley steering control unit located at a front end of the trolley and connected to the structure of the trolley orientably about a vertical axis that lies in the longitudinal median plane of the trolley;        a transmission connecting said steering control unit of the trolley to at least two of said wheel units; and        one or more locating supports arranged on said trolley structure for locating a piece container in position on said structure.        
Trolleys of the type referred to above have been used for a long time in industrial plants. Normally, the structure of the trolley is designed according to the dimensions and the configuration of the containers that are to be conveyed and the weight to be conveyed. More frequently, in an industrial plant different types of containers for pieces and consequently different configurations of trolley are used, each dedicated to a particular type of container.
In the past, there have also been proposed trolleys without a steering device, but having a structure that is adjustable in length and width, designed to enable adaptation to containers of different dimensions. Trolleys of this type are disclosed, for example, in documents DE 20 2004 001 688 U1 and DE 20 2008 007 158 U1.